Metal vapor rectifier



June 2, 1931. R. a. BERTHOLD 1,8 3,5 7

' METAL vAPoR RECTIFIER Fil ed July 11, 1928 Patented 1a.. 2,1931

UNITED STA nunonr e. naarnonn, or naanrn-smnnnssrm, (1mm, assrcnon. rosmmnnssonncxmu'wnm AKTIENGESEILSCEAFT, OF BERLIN-SIEHE'NSSTLD'I,GERMANY,

A CORPORATION OF GERMANY 'nE'raL varoa anc'rrrmn.

Application 111m m 11, 1928, Serial at.

My invention relates to improvements in metal vapor rectifiers, and morespecifically to rectifiers for convertingalternating current of highvoltage into direct current. The use of metal vapor rectifier plants forconverting alternating current of .high voltage into-direct current islimited by the comparatively low stopping voltage of such rectifiers.This stopping voltage is limited at the top by the following phenomenon:In the dis charge space of the rectifier are contained large quantitiesof ionized gas, consisting of positive (heavy) mercury ions and negative(light) electrons, which are continuously supplied by the constantlyburnin ignition arc, and are thus available indepen ent of a very shortlife of the ionization in all phases of the rectifying process.

If now in the stopping phase the rectifier anode becomes negative inrelation to the rectifier cathode, the existing positive mercury ionsoriginating from the ignition arc drop with a velocity correspondingwiththe great ti-ve face of the anode and directed away from it. Thiscurrent of vapor then also catches the ions streaming towards the anodedue to' the electricfield, and thus prevents the excessive heating ofthe anode. During the time the anode carries the working current, thepositive ions are driven away from the anode due to its positivepotential, in any case with- I in the extent of the anode drop. Theartificially produced flow of vapor thus acts during this positive anodepotential. It appears, however, preferable not to let the stream-ofvapor extend itself'in the direction of flow of the positive ionssubstantially beyond the sphere of the anode drop, because It W111otherwise half wave in the same direction as the Y 291,819, i in GermanyJuly 15, may

attempt to destroy the condition of the quasie neutrality in the arcdischarge and might thus cause a comparatively high voltage loss 1n therectifier also in the. direction of the flow. If it is thus impossibleto produce an artificial stream of vapor within the range of the anodedrop sphere only, a controlled stream of vapor directed away from theanode may also be used according to myeinvention, which streams from theanode towards the cathode during that half wave of the feedingalternating currentonly, during which the anode carries no current.

Mercury vapor rectifiers are already known in which in order to avoidbackfiring the anode ishoused in a chamber, which stands under a lowerdischarge cham er. To. obtain this lower pressure the anode is envelo dby a shell open towards the cathode an the outer face of this shell isswept by a stream of vapor directed towards the cathode. This stream ofvapor then exerts an exhausting action on the inside of the shellsurrounding the anode. In contrast with this arrangement it is ac-,cording to my invention not intended to prevent the backfiring by anincrease of the .vac-

-uum at the active anode face, but by a current of vapor directed awayfrom the anode face. While in the known arrangement the impingmg of gasions on the anodeis to be reduced by mcreaslng the vacuum, the positivegas ions flowing towards the anode are accordmg to my invention blownaway by a countercurrent set up.

In the drawings aflixed hereto and forming part ofmy specification twoembodiments of my invention are illustrated by way of example.

Fig. 1 is a vertical section through one constructioirof my improvedrectifier, in diagrammatlc representation, and

ressure than the remaining Fig. 2, a vertical section through anotherconstruction ofv improved rectifier.

L1ke parts are indicated by likenumerals of reference in both figures ofthe drawings. Referring to Fig. 1, 1 is a mercury cathode ofa glassrectifier 2, and 3 the anode. The

anode 1s designed as a sieve, and mercury vapor is constantly suppliedto itand'trav erses the perforations ofthe 'sieve from back to front. Tobring this about I provide a mercurycup 4 in communication with thecathode 1 and in which mercury vapor is constantly generated by means ofan auxiliary heating arrangement. This heating arrangement consists inFig. 1 of a heating spiral 5 and the feeding battery 6. The mercuryvapor enerated in the cu 4 is conveyed to m the bac of the sieve ano eby means of the tube 7. For condensing the mercury vapor emanating fromthe cathode 1 as well as from r the anode 3 the rectifier bulb 2 is inits upper art surrounded with a jacket 8 traversed y a cooling medium.Referring to Fig. 2, it will be seen, that the mercury vapor stream orspray directed away from the anode face is generated during the 4 halfwave of the feeding alternating current, during which the anodecarriesno current; The anode is again designed as a sieve. The chamber at theback of the sieve communicates by the tube 18 with an auxiliary mercuryvapor rectifier bulb 10. This auxiliary mercury vapor rectifier bulb isfed with alternating current and possesses two mercury electrodes 11 and12, of which the electrode '12 acts as cathode.

- For this purpose an auxiliary discharge is maintained at the electrode12 by means of alternating voltage duringwhich the anode carries nocurrent.

3. In a metal vapor rectifier, in combination, a sieve-like anode,.andmeans for producing a stream of vapor passing through the perforationsof the anode sieve and directed away from the active anode face, saidmeans creating the flow of vapor only during that half wave of therectified alternating voltage during which the anode carries no current.

4. In a metal vapor rectifier, in combination, a sieve-like anode, anauxiliary rectifier bulb fed with alternating current, a connecting tubebetween the auxiliary rectifier bulb and the metal vapor rectifier, saidauxiliary rectifier adapted to generate a flow of vapor passing throughthe sieve-like anode of the metal vapor rectifier and directed away fromthe active anode face.

5. In a metal vapor rectifier, an anode designed as hollow body,sieve-like perforations in the active anode face, an auxiliary rectifierbulb fed with alternating current, a connecting tube between theauxiliary rectifier bulb and the metal vapor rectifier, said connectingtube opening into the cavity -of said anode. ,1

In testimon whereof I aflix my signature. UDOLF G. BERTHOLD.

the source of direct current 13 and at the electrode 14. Through theauxiliary rectifier bulb thus flow'in phase with the, for instance,positive half wave of the feeding alternating current from the electrode12 to the electrode 11 rushes of current, which also producecorresponding intermittent rushes of mercur vapor between the twoelectrodes. Thesepu sating streams of mercury vapor are thenalso'supplied'by the tube 18 to the anode? of the main mercury vaporrectifier and produce at it the desired flow of mercury vaporu It willbe understood that my improved metalvapor rectifier may be equi ped withknown ap aratus for controlling t e current between t e anode and thecathode:

Various changes and modifications may be made without departing from thespirit of I desire, therefore, that only such limitations should beplaced thereon as are imposed by r the prior art. y

' I- claim as my invention: 1. In a metal vapor rectifier in'combination, -a sieve-like anode, and means for producing a stream ofvapor'passing through the perforations of. the anode s'ieve and directedaway from the active anode face.

. 2. In' a metal vapor rectifier, means for my invention and thefollowing claims and generating a flow of vapor from the active-anodefdce of-the rectifier and directed away from it, said meanscreating theflow of vapor u only during that half'wave of the reetified

